The invention relates to a pivot bearing arrangement for doors of the type genrally disclosed in DOS (German Unexamined Laid-Open Application) 2,218,498, wherein a rotationally operable shaft journal of a door closer is to be joined for rotation with a journal extension, the free end of the latter carrying either a closer arm or a door. Thus, the shaft journal and the journal extension are connected so that they are mutually nonrotatable with respect to each other. By means of the shaft of the door closer being split up, the closer can be adapted in a simple way, to different mounting conditions, by attaching to the shaft journal a journal extension or journal adapter having a suitable length and a suitable structure of the coupling area, so that the unit can be coupled to the door.
In a door closer arrangement, the zones of the shaft journal and the journal extension which engage each other in a shape-mating fashion are exposed to a large and suddenly occurring torque load. Therefore, the shape-mating connection must be constructed so that it can reliably absorb great loads and so that it has no free play.
For this purpose, the conventional arrangement provides that the journal extension engages, with a non-circular base portion fashioned like a truncated pyramid, a corresponding recess of the shaft journal. This is done for the purpose of compensating for the unavoidable play due to the manufacturing tolerances. The truncated pyramid is forced in the manner of a wedge into a corresponding recess of the shaft journal. A disadvantage in this connection is the wedging force resulting therefrom, which force acts radially outwardly on the shaft journal. Another disadvantage is the depth of penetration which varies, depending on the tolerance condition. The tangentially aligned shape-mating surfaces likewise transmit force components, effective radially in the same direction and arising from the torque of the closer, to the annular wall of the shaft journal, and therefore this wall is exposed to a high and shock-like stress along the lines of the widening of the wall. In case of passive pivot bearings, i.e. those exerting merely a hinge function and intending to carry only the weight of the door, considerable transverse forces occur due to this door weight, which forces tend to tip the journal extension off the shaft journal.
The same load occurs, of course, in case of active pivot bearings, in addition to the load resulting from the torque transmission, if such pivot bearings of door closers also exert directly the hinge function. This is the case, for example, in most instances with pendulum-type door closers.
This tipping moment resulting from the weight of the door poses great requirements on the load carrying capacity of the tensioning element which is to hold the shaft journal and the journal extension in their engaged and axially aligned position.
Conventional tightening screw connections as shown, for example, in the aforementioned DOS No. 2,218,498, however, have only a low load-bearing capacity. In this prior art construction, a tightening screw is provided which rests with its flaring head section in the journal extension and is threadedly inserted with the threaded shank, which latter is, of course, of a reduced diameter as compared to the head section, in a corresponding threaded bore of the shaft journal. The head configuration of the journal extension, intended for being coupled to a door, is extensively standardized so that the spacing of the coupling surfaces serving here for the torque transmission with respect to the pivot axis is fixedly determined. Since, furthermore, the bore which receives the head section of the tightening screw in a countersunk manner must not rupture these coupling surfaces under any circumstances, the diameter of this bore and, thus, by force of circumstances, the thread diameter of the tightening screw are very strictly limited.
It is, therefore, an object of this invention to provide a pivot bearing arrangement of the aforementioned type which ensures an exact and high-load-bearing seat and shape-mating engagement of the journal extension at the shaft journal while simultaneously reducing the load on the shaft journal and ensuring a sufficient axial tightening force, consequently providing a reliable and permanent connection of the two parts.
This object has been attained with the use of the features set out in the present invention.
The shape-mating connection indicated herein corresponds to the conventional interlocking teeth connection known from German Patent No. 440,816 as "Hirth serrations", and the use of such serrations in accordance with this invention has now opened up a substantial simplification and improvement also in this sector of technology. The substantial advantage of these serrations resides in that this arrangement provides a positive coaxial guidance of the shaft journal with respect to the journal extension and, at the same time, the shape-mating connection is established which is necessary for torque transmission.
Any change in position of the journal extension with respect to the shaft journal leads, due to the special shape of the serrations, to an axial enlargement of the distance between the two parts, so that it is possible merely with the use of an axial tightening screw to secure the axially aligned position as well as to obtain the required rotational rigidity. The radial teeth extend to the outermost rim of the shaft, since no centering ring shoulder is required, so that high torques can be transmitted. During torque transmission, no radially effective force components are produced which could lead to a loosening of the shape-mating interconnection. The Hirth serrations employed, in accordance with this invention, thus make it possible to effect a shape-mating coupling of a shaft journal with a journal extension which can be permanently placed under high loads, wherein the load-bearing limit is determined essentially only by the strength of the anchoring of the tightening screw. Due to the threaded pin to be inserted into the two parts to be joined respectively, there is no longer the necessity of providing a supporting head. The shank diameter of the threaded pin to be inserted in the journal extension can, therefore, be selected to be at least as large as, therefore, the diameter of the supporting head. Consequently, the thread exhibits a significantly greater bearing capacity, and the two parts can be pressed against each other with a considerably greater tightening force.
Although the Hirth serrations per se are conventional (see German Patent No. 440,816), they have been utilized apparently only in the automobile manufacturing field. Also, the arrangement according to French Patent No. 1,533,301 is in the same field of art. This patent employs the Hirth serrations and secures the interlocking position thereof by means of an internally disposed tightening screw which can be threaded with an opposite pitch direction into the two crankshaft sections.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.